In recent years, the plan for putting the driving safety support systems to practical use with a vehicle communication device for inter-vehicle communication is examined. In this plan, an information-exchange type application for transmitting and receiving information of its own vehicle on a constant period among the respective vehicles is generally used.
However, when the number of vehicles existing in a communication area increases, congestion occurs due to the increase of communication traffic, so that the inter-vehicle communication cannot be sufficiently performed, and it is considered that this information-exchange type application cannot provide a safety assisting service.
Therefore, Patent Document 1 discloses a method of avoiding the congestion by performing a transmitting cycle control of its own vehicle based on a dangerous situation of a vehicle and the traffic volume of a channel so that the congestion may not occur in the inter-vehicle communication. Further, Patent Document 2 discloses a method of resetting reception sensitivity, transmission power, antenna directivity, and frequency of its own device on the basis of the danger degree of the vehicle so that the congestion may not occur in the inter-vehicle communication.    Patent Document 1: Japanese Patent Application Laid-Open No. 2006-209333    Patent Document 2: Japanese Patent Application Laid-Open No. 2004-206624
The vehicle communication device disclosed in Patent Document 1 and Patent Document 2 can deal with only a single application as the information-exchange type application, and cannot use other plurality of applications such as an emergency application. Also, the vehicle communication device disclosed in Patent Document 1 and Patent Document 2 cannot ensure a communication band for other plurality of applications such as the emergency application.
Furthermore, the vehicle communication device disclosed in Patent Document 1 and Patent Document 2 avoids the congestion by performing a communication control on only its own vehicle, but the traffic amount of the entire network cannot be immediately reduced only by the communication control of its own vehicle.